Dial Lamp Puzzle.

[Robert Darwent]

I always thought that the diode delivers half power therefore the voltage
Vout must be .707 of Vin, that was the basis of my last post, ie: 240 volts in 170 volts out, so R = 170 minus Vh divided by Ih (at 240v mains) dissipation being the usual I sqrd R

After a bit more thought I can follow your reasoning and see your method is equally valid. I stand corrected.

I think it basically amounts to the same thing.

Yes it does Lawrence.

Regards

[Alistair D]

Joe,
have you tried measuring the heater voltage. It could be a bit high and that would overrun the heaters.

Al

[Joe]

That's what was worrying me when the first lamp didn't last long.

The LT measures 6V, which is actually a bit low.

A closer examination will probably be worthwhile though.

Cheers

Joe

[Robert Darwent]

Joe,
have you tried measuring the heater voltage. It could be a bit high and that would overrun the heaters.

Al

Joe did say he'd measured the voltage across the dial bulb at 6V, but I'm not sure what the heater voltage is in the radiogram. Presumably 6.3V?

Regards

[Joe]

I don't have a circuit diagram for that set but the valves (6K8GT, ECH35, EBL31) are all rated at 6.3V. It may be instructive to leave a voltmeter connected for a long time just to make sure that it doesn't rise over time. I use it a lot so there'll be plenty of opportunities.

- Joe

[Alistair D]

I must try reading previous posts.
I must try reading previous posts.
I must try reading previous posts.
I must try reading previous posts.
etc.

Al